Normally I can't stand this kind of game for more than a few minutes. EleMental was pretty good, though - I kept playing for a lot longer than I intended, considering my intent was just to check it out.
Ok, I have a few comments about the interface:
1) When you start playing, if you destroy multiple tiles in a single move, you'll get multiple help screens. That way, you can't really tell what tile combination triggered a help screen and you could end missing the idea, because the help you get isn't be connected to any specific thing you did.
2) The help system needs a screen about how to deal with monsters. (Maybe I missed it the first time, by destroying multiple tiles? I'd give more info, but the second time I started the game, the help screens didn't show and I can't replicate the problem.)
3) The different kinds of objective have different levels of priority for the player. For instance, when a monster comes, I want to deal with it ASAP, and not try to collect a certain kind of tile to level up. If I'm dead, leveling up doesn't matter.
Perhaps you should group objectives by urgency, or mark their "type" in a distinguishing way. Perhaps even different pools for different types of objective.
4) Make the state of each option clear in the menu (whether it is ON or OFF). For instance, I couldn't tell if hints were being shown or not after playing with the configs for a while.
5) By default, the tile legend appears over the message box. It would be best if each interface component had its own place on the screen.
6) Actually, it would be better if you only kept what the player needs to play on the main game screen. For instance, the menu could be moved to a pop-up window (such as the one you already use for the credits). Also, perhaps the "menu pop-up" could be called by the ESC key, instead of having it quit the application without asking for a confirmation.
7) The tile legend is useful (especially the first time you play), but it is taking way too much space on-screen. Maybe you could scale it down a little bit or move it out of the way (say, place the legend in a frame around the board, so that when the player doesn't need it anymore, it becomes part of the decoration).
8 ) You should probably place the achievement messages where the player is looking (that is, over the board). Also, instead of having cards "fall" into the pool they belong to, it would be even better to have cards spawn from the tiles you destroyed. That way, it is even easier for starting players to understand what spawns what, and the veteran player doesn't need to look away from the board to check what card he has taken.
9) The help pop-up for the inventory items is taking a bit too long to appear.
10) The help pop-up for the cards at the bottom of the screen is redundant.
11) Aren't red cards "items" too? I have red card "swords" and inventory "swords"...
12) Consider using tiles in the objective cards instead of using text. For instance, instead of "Collect Runes in this order: Earth Fire Fire Fire", do something like "Collect Runes in this order: <Earth tile image> <Fire tile image> <Fire tile image> <Fire tile image>". That way, it is easier to identify what needs to be done. Also, it's a nice touch.
13) I had "X" turns to move a chaos tile to a marker. At the last turn, while the card was still showing at the objective pool, I managed to move the tile to the marker, but still received a "Failed!" message. My point is, the way it is, I was pursuing an objective I couldn't complete anymore. I'm not sure about this, but it seems like there is a "check this on the start of a turn"/"check this on the end of a turn" issue.
In resume, the game is pretty good, but I was constantly pulled away from the toy (matching the tiles) to check what I had to do, or had too many places to look at and ended missing what was happening (like achievement messages). If I had to change a single thing, it would be the way things are arranged in the interface. I hope this helps.